1. Field of the Invention
The present invention relates generally to a pulse signal amplifier, and is directed more particularly to a pulse signal amplifier in which the leakage current from an inductive load is prevented from flowing to the base-emitter circuit of an output transistor.
2. Description of the Prior Art
In the art there has been known, as a pulse signal amplifier which amplifies a pulse width modulated signal, the U.S. Pat. No. 4,021,748 entitled in "Amplifier with Field Effect Transistors Having Triode-type Dynamic Characteristics," assigned to the SONY CORPORATION and issued on May 3, 1977, in which an FET (field effect transistor) is used. According to the U.S. Patent, the switching frequency can be made high such as several hundreds KH.sub.z but it is rather expensive.
To avoid this defect, it may be considered that a bi-polar transistor, which is relatively low at cost and connected in an emitter-follower configuration, is used as a switching element. In this case, however, since its drive circuit becomes complicated and the bypass current from an inductive load is leaked through the base-emitter circuit of an output transistor, power loss can not be reduced even through the amplifier is a switching mode amplifier.